An annealing process is a heat treatment of a wafer in order to modify properties of materials/structures processed on its surface or in the bulk. For example, annealing is performed on the wafer in order to activate certain species (dopants) of a device such as, for example, associated with a transistor. Depending on the structures or dopants to be annealed, the temperatures necessary for such annealing process can range upwards of 1000° K in some applications and much lower temperatures in other applications.
Annealing can be performed by many different processes. For example, a rapid thermal annealing (RTA) of a wafer can be performed in an oven at high temperatures. In such applications, the entire structure and all materials on the surface are subject to an anneal at the same temperature. However, the anneal temperature for one device or structure may not be applicable for another device or structure, resulting in damage to some devices or structures. This process also has a large temperature ramp up time which increases processing times and costs.
Another annealing process is a laser anneal. In this process, for example, an excimer laser is used to anneal structures/materials on the wafer. This annealing process has a large temperature ramp up time and duration and a non-uniform temperature distribution, which causes limitations for species activation/device performance. For example, the laser has a large beam resolution on the order of about 500 μm2 which makes it impractical for use with smaller areas requiring an anneal. As such, using a laser annealing process may damage structures close to the anneal. Also, as the beam is known to diverge due to reflection, it is possible to cause a non-uniform anneal.
In yet another annealing process, it is possible to place a resistor on a back end of line (BEOL) device in order to anneal a front end of line (FEOL) device. In such applications, though, it is difficult to control the heating and, as a result, it is possible to damage the FEOL device during the annealing process. Typically, such annealing method is only good for large FEOL devices.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.